As display devices usable for electric appliances and electronic devices, a liquid crystal display device using an electro-optical effect of a liquid crystal material and an organic EL (electroluminescence) display device including an organic electroluminescence (EL) element have been developed. Such a display device includes a display screen formed of a plurality of pixels provided on a substrate. Each of the plurality of pixels of the display device includes a liquid crystal element, an organic electroluminescence element or the like as a display element. In the display device, such pixels arrayed in a display region are driven by a pixel circuit and a driving circuit each including a transistor, and thus a signal is input and a moving image or a still image is displayed.
In the case where an organic EL element is used as the display element, a sealing layer is provided so as to cover an organic light emitting layer. For example, Japanese Laid-Open Patent Publication No. 2016-046126 discloses that such a sealing layer prevents permeation of moisture or oxygen into an organic light emitting layer.
In the meantime, a touch panel, which is a display device including a display element and a touch sensor provided on the display element, has been rapidly spread recently. Such a touch panel is now indispensable for mobile information terminals such as smartphones and the like, and is progressively developed worldwide for further improvement in the information society.
Methods for manufacturing such a touch panel are classified into two systems: one is an out-cell system, by which a touch sensor is manufactured separately from a display device and then the touch sensor and the display device are bonded together, and the other is an in-cell system, by which a touch panel is incorporated into a display device.